Coaxial cables have an inner electrical conductor, referred to herein simply as a “core,” an outer electrical conductor, referred to herein simply as a “shield” which is concentrically disposed around the core, an inner dielectric disposed between the core and the shield, and a protective outer covering, referred to simply herein as the “jacket.” Coaxial cables are used widely in the electrical arts, for example to send radio frequency (RF) from one electrical component to another. The shield provides the dual function of guiding the RF energy within the coaxial cable without allowing its escape to the outside, while preventing external RF energy from entering.
By way of exemplification of a coaxial cable, the core and shield together form a conduit for the transmission of RF energy which travels through the dielectric, not the core (that is, the inner conductor). The principal purpose of the shield is to guide the traveling wave. Because RF current flows only on the surfaces of conductors, the shield (that is, the outer conductor) can provide the secondary function of shielding, because internal and external currents can exist simultaneously and separately on opposite surfaces. The shield is usually connected to a chassis or to earth ground, but need not be. The jacket is often made of plastic, which is also dielectric, but it can be any material, including metal, wherein its function is mechanical and has no relation to its dielectric properties.
Frequently, it is desirable to connect one end of a coaxial cable to a circuit board, also referred to commonly as a printed circuit board. In this regard, the circuit board includes a substrate, a plurality of electrical devices interfaced with the substrate through holes (vias) in the substrate, and conductive pathways on the substrate for providing electrical connections with respect to the interfaced devices.
A crimp terminal has been used in the prior art for connecting one end of a coaxial cable to a circuit board. As shown at FIG. 1, the inner dielectric 10, the shield 12 and the jacket 14 are removed from an end section 16a of a coaxial cable 16 to provide a naked core section 18a of the core 18. This naked core section 18a, which may be solder coated, is then used to solder to a connection location of the circuit board. A second end section 16b of the coaxial cable has the jacket and shield removed, thereby providing a naked inner dielectric section 10a of the inner dielectric 10. A third end section (not visible) of the coaxial cable has the jacket removed, thereby providing a naked shield section 12a of the shield 12. A crimp terminal 20 is then crimped onto the naked shield section 12a, and may be soldered thereto and further may be crimped by wings 22 to the adjacent intact jacket 14. The crimp terminal 20 has shield connection features 24, such as a plurality of blades (as shown) or a plurality of protruding wires, for being electrically connected to appropriate locations of the circuit board.
Several drawbacks of using a crimp terminal for connecting a coaxial cable end to a circuit board, include: portions of the crimp terminal protruding in relation to the circuit board, creating radiated interference issues and RF coupling to the board's opposite side; core location on the circuit board is not reproducibly precise nor robust, thereby introducing impedance variation and risking connection failure; making the electrical connections to the wire section and shield connection features is difficult; and, crimping of the shield can have inconsistent RF performance with regard to the individual crimps of a number of made crimps.
Accordingly, what remains needed in the art is a termination of an end of a coaxial cable which can effect a reliable connection to a circuit board without any of the drawbacks of the prior art.